Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, exhaust a complex mixture of combustion related constituents. The constituents may be gaseous and solid material, which include nitrous oxides (NOx) and particulate matter. Due to increased attention on the environment, exhaust emission standards have become more stringent and the amount of NOx and particulate matter emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
Engineers have come to recognize that common rail fuel systems may be used to improve diesel engine emissions and performance. Common rail fuel systems can provide high injection pressure, flexible injection modes, such as multiple injections, and may be operated independently of engine speed. However, because of the high pressures associated with common rail fuel systems, the same may have an increased risk of fuel leakage. Leakage of fuel at high pressures tends to generate heat, which is then transferred to the injector components. This heat may increase the temperature and may change the material properties of the injector components. In certain instances, the temperature may become high enough to cause fuel to decompose and become unstable or oxidated within the high-pressure fuel system. This may lead to fuel deposits being formed on injector components, such as control valves. These deposits may inhibit the movement of control valve components by causing the same to become sticky or stuck. This may lead to control valve failure and ultimately injector failure.
To meet increasingly stringent emissions regulations, engine manufacturers have utilized multiple injections of fuel into the combustion chamber during any particular combustion event. The multiple injections may include a pilot injection, a main injection, and/or a post injection. In most cases, multiple injections may be achieved by controlling the actuation of a control valve multiple times during any given combustion cycle. In order to achieve these multiple actuation events, additional electrical energy is required. The increased number of valve actuations may lead to more leakage of high-pressure fuel within the fuel injector. Increased leakage may further increase the internal temperature of an injector.
The use of multiple injection events and higher fuel pressures may have a significant impact on the magnitude of the heat energy to which components of fuel injections. One of the hottest locations within a fuel injector is the high-pressure leak split spot. This spot is located at or near the center of a control valve. Rising temperatures within a control valve may lead to failure of solenoids if the fuel injector is not cooled sufficiently. It would be desirable to cool a fuel injector in such a manner that the temperature of the high-pressure leak split spot is controlled.
An example of a previous attempt to cool a fuel injector is disclosed in U.S. Pat. No. 6,360,963 to Popp. In that disclosure, openings in the form of the cross holes are drilled into the sleeve of the needle chamber. These cross-holes are provided to allow gaseous fuel to cool the exposed surface of the needle valve. While this disclosure may work to keep the injector needle and tip cooler, it does nothing to address the temperature within the hottest location of the injector; the high-pressure leak split spot. Thus, the control valve may still be susceptible to failure due to excessive temperatures.
The disclosed fuel injector and control valve assembly with thermal load control is directed to overcoming one or more of the problems set forth above.